調試我的ifelse語句時遇到問題

我無法通過ifelse語句獲得預期結果，該語句用於將大學數據解析爲在學期內/期間內/學期間斷開，在數據框中創建一個新列refstats$Semester。調試我的ifelse語句時遇到問題

下面是一些樣本數據和我的部分代碼，我想/希望的問題是：

Date<-c('2009-04-12','2009-07-07','2009-08-09','2009-08-20','2009-08-25','2009-08-30','2020-09-03','2009-09-07','2009-11-15','2009-11-22','2009-12-05','2009-12-12','2010-01-02','2010-01-18','2010-02-14','2010-03-22','2010-05-23','2010-06-13','2010-06-19','2010-08-08','2010-09-05','2010-12-09','2011-03-27','2011-08-06','2011-12-09','2012-06-10','2013-01-20','2013-01-21','2013-05-10','2013-08-03','2013-12-14','2014-05-22','2015-03-20','2015-08-20','2015-11-30','2015-12-15','2016-01-10','2016-02-15') 

# create data frame 
refstats<-data.frame(Date) 

# convert Date to a Date object for evaluation in nested ifelse statement 
refstats$Date <- as.Date(refstats$Date, format = '%Y-%m-%d') 

# ---- determine Semester, broken up into school year ifelse statments 
# because R gets confused if the ifelse is too deeply nested. 

# dummvar is just something to do in the final else condition, so it doesn't 
# overwrite the correct Semester once it is found. 

# 2009-2010 
ifelse(refstats$Date >= as.Date("2009-08-24") & refstats$Date <= as.Date("2009-09-06"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2009-09-07") & refstats$Date <= as.Date("2009-09-07"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2009-09-08") & refstats$Date <= as.Date("2009-11-20"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2009-11-21") & refstats$Date <= as.Date("2009-11-29"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2009-11-30") & refstats$Date <= as.Date("2009-12-10"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2009-12-11") & refstats$Date <= as.Date("2009-12-18"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2009-12-19") & refstats$Date <= as.Date("2010-01-18"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2010-01-19") & refstats$Date <= as.Date("2010-03-19"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2010-03-20") & refstats$Date <= as.Date("2010-03-28"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2010-03-29") & refstats$Date <= as.Date("2010-05-06"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2010-05-07") & refstats$Date <= as.Date("2010-05-14"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2010-05-15") & refstats$Date <= as.Date("2010-05-16"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2010-05-17") & refstats$Date <= as.Date("2010-06-12"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2010-06-13") & refstats$Date <= as.Date("2010-06-13"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2010-06-14") & refstats$Date <= as.Date("2010-08-07"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2010-08-08") & refstats$Date <= as.Date("2010-08-22"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))) 

# 2010-2011 
ifelse(refstats$Date >= as.Date("2010-08-23") & refstats$Date <= as.Date("2010-09-05"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2010-09-06") & refstats$Date <= as.Date("2010-09-06"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2010-09-07") & refstats$Date <= as.Date("2010-11-19"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2010-11-20") & refstats$Date <= as.Date("2010-11-28"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2010-11-29") & refstats$Date <= as.Date("2010-12-09"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2010-12-10") & refstats$Date <= as.Date("2010-12-17"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2010-12-18") & refstats$Date <= as.Date("2011-01-17"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2011-01-18") & refstats$Date <= as.Date("2011-03-18"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2011-03-19") & refstats$Date <= as.Date("2011-03-27"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2011-03-28") & refstats$Date <= as.Date("2011-05-05"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2011-05-06") & refstats$Date <= as.Date("2011-05-13"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2011-05-14") & refstats$Date <= as.Date("2011-05-15"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2011-05-16") & refstats$Date <= as.Date("2011-06-11"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2011-06-12") & refstats$Date <= as.Date("2011-06-12"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2011-06-13") & refstats$Date <= as.Date("2011-08-06"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2011-08-07") & refstats$Date <= as.Date("2011-08-21"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))) 

# 2011-2012 
ifelse(refstats$Date >= as.Date("2011-08-22") & refstats$Date <= as.Date("2011-09-04"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2011-09-05") & refstats$Date <= as.Date("2011-09-05"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2011-09-06") & refstats$Date <= as.Date("2011-11-18"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2011-11-19") & refstats$Date <= as.Date("2011-11-27"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2011-11-28") & refstats$Date <= as.Date("2011-12-08"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2011-12-09") & refstats$Date <= as.Date("2011-12-16"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2011-12-17") & refstats$Date <= as.Date("2012-01-16"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2012-01-17") & refstats$Date <= as.Date("2012-03-16"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2012-03-17") & refstats$Date <= as.Date("2012-03-25"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2012-03-26") & refstats$Date <= as.Date("2012-05-03"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2012-05-04") & refstats$Date <= as.Date("2012-05-11"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2012-05-12") & refstats$Date <= as.Date("2012-05-13"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2012-05-15") & refstats$Date <= as.Date("2012-06-09"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2012-06-10") & refstats$Date <= as.Date("2012-06-10"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2012-06-11") & refstats$Date <= as.Date("2012-08-04"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2012-08-05") & refstats$Date <= as.Date("2012-08-26"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))) 

# 2012-2013 note this year has MLK day within Spring Semester 
ifelse(refstats$Date >= as.Date("2012-08-27") & refstats$Date <= as.Date("2012-09-02"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2012-09-03") & refstats$Date <= as.Date("2012-09-03"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2012-09-04") & refstats$Date <= as.Date("2012-11-16"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2012-11-17") & refstats$Date <= as.Date("2012-11-25"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2012-11-26") & refstats$Date <= as.Date("2012-12-13"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2012-12-14") & refstats$Date <= as.Date("2012-12-20"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2012-12-21") & refstats$Date <= as.Date("2013-01-13"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2013-01-14") & refstats$Date <= as.Date("2013-01-20"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2013-01-21") & refstats$Date <= as.Date("2013-01-21"), refstats$Semester<-"MLK Day" , 
    ifelse(refstats$Date >= as.Date("2013-01-22") & refstats$Date <= as.Date("2013-03-15"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2013-03-16") & refstats$Date <= as.Date("2013-03-24"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2013-03-25") & refstats$Date <= as.Date("2013-05-02"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2013-05-03") & refstats$Date <= as.Date("2013-05-10"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2013-05-11") & refstats$Date <= as.Date("2013-05-12"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2013-05-13") & refstats$Date <= as.Date("2013-06-08"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2013-06-09") & refstats$Date <= as.Date("2013-06-09"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2013-06-10") & refstats$Date <= as.Date("2013-08-03"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2013-08-04") & refstats$Date <= as.Date("2013-08-25"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))))) 

# 2013-2014 
ifelse(refstats$Date >= as.Date("2013-08-26") & refstats$Date <= as.Date("2013-09-01"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2013-09-02") & refstats$Date <= as.Date("2013-09-02"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2013-09-03") & refstats$Date <= as.Date("2013-11-22"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2013-11-23") & refstats$Date <= as.Date("2013-12-01"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2013-12-02") & refstats$Date <= as.Date("2013-12-12"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2013-12-13") & refstats$Date <= as.Date("2013-12-20"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2013-12-21") & refstats$Date <= as.Date("2014-01-20"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2014-01-21") & refstats$Date <= as.Date("2014-03-21"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2014-03-22") & refstats$Date <= as.Date("2014-03-30"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2014-03-31") & refstats$Date <= as.Date("2014-05-08"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2014-05-09") & refstats$Date <= as.Date("2014-05-16"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2014-05-17") & refstats$Date <= as.Date("2014-05-18"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2014-05-19") & refstats$Date <= as.Date("2014-06-14"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2014-06-15") & refstats$Date <= as.Date("2014-06-15"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2014-06-16") & refstats$Date <= as.Date("2014-08-09"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2014-08-10") & refstats$Date <= as.Date("2014-08-24"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))) 

# 2014-2015 
ifelse(refstats$Date >= as.Date("2014-08-25") & refstats$Date <= as.Date("2014-08-31"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2014-09-01") & refstats$Date <= as.Date("2014-09-01"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2014-09-02") & refstats$Date <= as.Date("2014-11-21"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2014-11-22") & refstats$Date <= as.Date("2014-11-30"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2014-12-01") & refstats$Date <= as.Date("2014-12-11"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2014-12-12") & refstats$Date <= as.Date("2014-12-19"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2014-12-20") & refstats$Date <= as.Date("2015-01-19"), refstats$Semester<-"Winter Break" , 
    ifelse(refstats$Date >= as.Date("2015-01-20") & refstats$Date <= as.Date("2015-03-20"), refstats$Semester<-"Spring" , 
    ifelse(refstats$Date >= as.Date("2015-03-21") & refstats$Date <= as.Date("2015-03-29"), refstats$Semester<-"Spring Break" , 
    ifelse(refstats$Date >= as.Date("2015-03-30") & refstats$Date <= as.Date("2015-05-07"), refstats$Semester<-"Spring", 
    ifelse(refstats$Date >= as.Date("2015-05-08") & refstats$Date <= as.Date("2015-05-15"), refstats$Semester<-"Spring Finals" , 
    ifelse(refstats$Date >= as.Date("2015-05-16") & refstats$Date <= as.Date("2015-05-17"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2015-05-18") & refstats$Date <= as.Date("2015-06-13"), refstats$Semester<-"Summer I" , 
    ifelse(refstats$Date >= as.Date("2015-06-14") & refstats$Date <= as.Date("2015-06-14"), refstats$Semester<-"Closed" , 
    ifelse(refstats$Date >= as.Date("2015-06-15") & refstats$Date <= as.Date("2015-08-08"), refstats$Semester<-"Summer II" , 
    ifelse(refstats$Date >= as.Date("2015-08-09") & refstats$Date <= as.Date("2015-08-23"), refstats$Semester<-"Summer Break" , 
    dummvar<-NA)))))))))))))))) 

# 2015- 
ifelse(refstats$Date >= as.Date("2015-08-24") & refstats$Date <= as.Date("2015-09-06"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2015-09-07") & refstats$Date <= as.Date("2015-09-07"), refstats$Semester<-"Labor Day" , 
    ifelse(refstats$Date >= as.Date("2015-09-08") & refstats$Date <= as.Date("2015-11-20"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2015-11-21") & refstats$Date <= as.Date("2015-11-29"), refstats$Semester<-"Fall Break" , 
    ifelse(refstats$Date >= as.Date("2015-11-30") & refstats$Date <= as.Date("2015-12-10"), refstats$Semester<-"Fall" , 
    ifelse(refstats$Date >= as.Date("2015-12-11") & refstats$Date <= as.Date("2015-12-18"), refstats$Semester<-"Fall Finals" , 
    ifelse(refstats$Date >= as.Date("2015-12-19") & refstats$Date <= as.Date("2016-01-18"), refstats$Semester<-"Winter Break" , 
    dummvar<-NA))))))) 

refstats

我本來期望的最終聲明打印的東西，看起來像：

日期學期
2009-04-12 NA
2009-07-07 NA
2009-08-09 NA
2009-08-20 NA
2009-08-25秋季
2009-08-30秋季
2020年9月3日NA
2009-09-07勞動節
2009-11-15秋季
2009-11-22跌破
2009-12-05秋季
2009-12-12秋季總決賽
2010-01-02寒假
2010-01-18寒假
2010-02-14春天
2010-03-22春假
2010-05-23夏天我
2010-06-13關閉
2010-06-19夏季II
2010-08-08暑假
2010-09-05秋季
2010-12-09秋季
2011-03-27春假
2011-08-06夏季II
2011-12-09跌破
2012-06-10夏天我
2013年1月20日春節
2013-01- 21 MLK日
2013 -05-10春季總決賽
2013年8月3日暑期II
2013-12-14秋季總決賽
2014年5月22日夏季我
2015年3月20日春季
2015年8月20日暑假
2015年11月30日秋季
2015年12月15日秋季總決賽
2016年1月10日寒假
2016年2月15日NA

相反，refstats$Semeseter是所有的「寒假」

任何關於我如何誤入歧途的想法或建議，或者對問題有更好的解決方法？我最後一個問題與此有關 - 我仍然在努力去理解。

刪除了一些中間嘗試解決問題，讓我留在30,000 characther限制

第三次嘗試，加入as.Date：

我不得不更換我的初始代碼（由於要求問題的字符數限制爲30,000個） - 所以新代碼位於頂部，as.Date在那裏。

唉！現在我又回到了「冬日休息」再次出現的一切！

第四次嘗試，試圖用findInterval：

Date<-c('2009-04-12','2009-07-07','2009-08-09','2009-08-20','2009-08-25','2009-08-30','2020-09-03','2009-09-07','2009-11-15','2009-11-22','2009-12-05','2009-12-12','2010-01-02','2010-01-18','2010-02-14','2010-03-22','2010-05-23','2010-06-13','2010-06-19','2010-08-08','2010-09-05','2010-12-09','2011-03-27','2011-08-06','2011-12-09','2012-06-10','2013-01-20','2013-01-21','2013-05-10','2013-08-03','2013-12-14','2014-05-22','2015-03-20','2015-08-20','2015-11-30','2015-12-15','2016-01-10','2016-02-15') 

Semester<-c('NA','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','MLK Day','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','Spring','Spring Break','Spring','Spring Finals','Closed','Summer I','Closed','Summer II','Summer Break','Fall','Labor Day','Fall','Fall Break','Fall','Fall Finals','Winter Break','NA') 
StartDate<-c('1000-01-01','2009-08-24','2009-09-07','2009-09-08','2009-11-21','2009-11-30','2009-12-11','2009-12-19','2010-01-19','2010-03-20','2010-03-29','2010-05-07','2010-05-15','2010-05-17','2010-06-13','2010-06-14','2010-08-08','2010-08-23','2010-09-06','2010-09-07','2010-11-20','2010-11-29','2010-12-10','2010-12-18','2011-01-18','2011-03-19','2011-03-28','2011-05-06','2011-05-14','2011-05-16','2011-06-12','2011-06-13','2011-08-07','2011-08-22','2011-09-05','2011-09-06','2011-11-19','2011-11-28','2011-12-09','2011-12-17','2012-01-17','2012-03-17','2012-03-26','2012-05-04','2012-05-12','2012-05-15','2012-06-10','2012-06-11','2012-08-05','2012-08-27','2012-09-03','2012-09-04','2012-11-17','2012-11-26','2012-12-14','2012-12-21','2013-01-14','2013-01-21','2013-01-22','2013-03-16','2013-03-25','2013-05-03','2013-05-11','2013-05-13','2013-06-09','2013-06-10','2013-08-04','2013-08-26','2013-09-02','2013-09-03','2013-11-23','2013-12-02','2013-12-13','2013-12-21','2014-01-21','2014-03-22','2014-03-31','2014-05-09','2014-05-17','2014-05-19','2014-06-15','2014-06-16','2014-08-10','2014-08-25','2014-09-01','2014-09-02','2014-11-22','2014-12-01','2014-12-12','2014-12-20','2015-01-20','2015-03-21','2015-03-30','2015-05-08','2015-05-16','2015-05-18','2015-06-14','2015-06-15','2015-08-19','2015-08-24','2015-09-07','2015-09-08','2015-11-21','2015-11-30','2015-12-11','2015-12-19','2016-01-19') 
EndDate<-c('2009-08-23','2009-09-06','2009-09-07','2009-11-20','2009-11-29','2009-12-10','2009-12-18','2010-01-18','2010-03-19','2010-03-28','2010-05-06','2010-05-14','2010-05-16','2010-06-12','2010-06-13','2010-08-07','2010-08-22','2010-09-05','2010-09-06','2010-11-19','2010-11-28','2010-12-09','2010-12-17','2011-01-17','2011-03-18','2011-03-27','2011-05-05','2011-05-13','2011-05-15','2011-06-11','2011-06-12','2011-08-06','2011-08-21','2011-09-04','2011-09-05','2011-11-18','2011-11-27','2011-12-08','2011-12-16','2012-01-16','2012-03-16','2012-03-25','2012-05-03','2012-05-11','2012-05-13','2012-06-09','2012-06-10','2012-08-04','2012-08-26','2012-09-02','2012-09-03','2012-11-16','2012-11-25','2012-12-13','2012-12-20','2013-01-13','2013-01-20','2013-01-21','2013-03-15','2013-03-24','2013-05-02','2013-05-10','2013-05-12','2013-06-08','2013-06-09','2013-08-03','2013-08-25','2013-09-01','2013-09-02','2013-11-22','2013-12-01','2013-12-12','2013-12-20','2014-01-20','2014-03-21','2014-03-30','2014-05-08','2014-05-16','2014-05-18','2014-06-14','2014-06-15','2014-08-09','2014-08-24','2014-08-31','2014-09-01','2014-11-21','2014-11-30','2014-12-11','2014-12-19','2015-01-19','2015-03-20','2015-03-29','2015-05-07','2015-05-15','2015-05-17','2015-06-13','2015-06-14','2015-08-08','2015-08-23','2015-09-06','2015-09-07','2015-11-20','2015-11-29','2015-12-10','2015-12-18','2016-01-18','3000-01-01') 


# create data frames 
refstats<-data.frame(Date) 
calendar<-data.frame(Semester,StartDate,EndDate) 

# convert Date to a Date object for evaluation in nested ifelse statement 
refstats$Date <- as.Date(refstats$Date, format = '%Y-%m-%d') 
calendar$StartDate <- as.Date(calendar$StartDate, fromat = '%Y-%m-%d') 
calendar$EndDate <- as.Date(calendar$EndDate, fromat = '%Y-%m-%d') 

# determine semester of each refstats$Date, by reference dataframe containing calendar 
# of school year dates. calendar$EndDate is not really used, because the 
# findInterval function defaults to left-closed intervals so only need to use StartDate: 
refstats$Semester <- calendar$Semester[ findInterval(refstats$Date, calendar$StartDate)]

起初，這產生的錯誤消息$<-.data.frame錯誤（*tmp*，「學期」，值= C（2L，2L，13L ，：替換有34行，數據有38

我的數據有一些超出範圍的值，因此我添加了一個返回的開始間隔到1000年，結束時間間隔達到3000年。它的工作原理！

來源

2014-12-18 Steve T

您比較數值（這是什麼日期，歸類變量）爲字符值。 – 2014-12-18 22:55:06

我已經添加替換代碼在我的問題的底部，以' '在ifelse聲明中刪除，代碼運行，但沒有找到匹配的日期 - 我還在比較蘋果和橘子嗎？ – 2014-12-18 23:10:44

在控制檯輸入'2015-12-19'沒有引號，看看你得到了什麼。 – 2014-12-18 23:12:11

你沒有解決的邏輯問題。你的第一次約會之前的日期怎麼樣？

> dt2009_10 <- scan(what="") 
1: '2009-08-24' 
2: '2009-09-07' 
3: '2009-09-08' 
4: '2009-11-21' 
5: '2009-11-30' 
6: '2009-12-11' 
7: '2009-12-19' 
8: '2010-01-19' 
9: '2010-03-20' 
10: '2010-03-29' 
11: '2010-05-07' 
12: '2010-05-15' 
13: '2010-05-17' 
14: '2010-06-13' 
15: '2010-06-14' 
16: '2010-08-08' 
17: 
Read 16 items 

> nam2009_10 <- c("Fall" , 
+ "Labor Day" , 
+ "Fall" , 
+ "Fall Break" , 
+ "Fall" , 
+ "Fall Finals" , 
+ "Winter Break" , 
+ "Spring" , 
+ "Spring Break" , 
+ "Spring" , 
+ "Spring Finals" , 
+ "Closed" , 
+ "Summer I" , 
+ "Closed" , 
+ "Summer II" , 
+ "Summer Break")

我不會做所有的工作，建立了多年的一組值，而是將演示如何避免使用嵌套ifelse語句。 findInterval函數默認爲左閉區間，所以我們可以使用我提取並放入dt2009_10的一組初始值。然後comapre您的日期，歸類日期變量，使用的一個索引，我投入nam2009_10區間的名字：

nam2009_10[ findInterval(refstats$Date, as.Date(dt2009_10)) ] 
[1] "Fall"   "Fall"   "Summer Break" "Labor Day" "Fall"   
[6] "Fall Break" "Fall"   "Fall Finals" "Winter Break" "Winter Break" 
[11] "Spring"  "Spring Break" "Summer I"  "Closed"  "Summer II" 
[16] "Summer Break" "Summer Break" "Summer Break" "Summer Break" "Summer Break" 
[21] "Summer Break" "Summer Break" "Summer Break" "Summer Break" "Summer Break" 
[26] "Summer Break" "Summer Break" "Summer Break" "Summer Break" "Summer Break" 
[31] "Summer Break" "Summer Break" "Summer Break" "Summer Break"

因爲我沒有做2010-11，或以後的歲月裏，所有的較後日期出現瞭如暑假」。

然後

來源

2014-12-18 23:10:09

在OP的前一個問題（在同一主題上），我指出他[我的答案]（http://stackoverflow.com/questions/27045753/how-to-classify-a-given-date-time例如夏季秋季），我使用了'findInterval'。我仍然認爲這是「解決問題的更好方法」。 – Henrik 2014-12-18 23:28:05

「你沒有解決的一個邏輯問題，在你的第一次約會之前的日期呢？」我認爲這將最終成爲NA值。我現在正試圖理解'findInterval'方法，並且如果我能弄明白，就會用修改後的代碼更新我的問題。我不知道「前一個OP的問題」是什麼意思 - 也許這是指我以前的問題？什麼是OP？ – 2014-12-18 23:57:45

OP ==「原創海報」。這是新聞組俚語。 – 2014-12-19 00:01:22

調試我的ifelse語句時遇到問題

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